enabling middle-button paste in sagemath's jupyter

edit

I am running sagemath 9.8 with jupyter_core 4.11.2 and jupyter_client 7.4.4. I access the sagemath notebook in firefox 116.0.2 on an Ubuntu 22.04 machine. I would like to enable middle-button paste in the jupyter notebook. My understanding from stack overflow is that this requires that sagemath's jupyter use codemirror 5.44.0. The file $SAGE_ROOT/local/var/lib/sage/venv-python3.10.8/lib/python3.10/site-packages/notebook/static/components/codemirror/src/edit/main.js reports that the codemirror version is 5.56.0 so I am not sure why middle button paste is not working. In firefox about:config, I do have middlemouse.paste = True. Is there another firefox setting that I need to change?